The invention relates to a device for feeding curable, liquid containing material, especially residual concrete, residual mortar, and the like, into, through and out of the feeding device and thereafter to a separator for separating the material into defined individual components.
Devices of this type are employed, for example, in ready-mix concrete works and are used to take up unset residues of curable material, such as concrete, mortar and the like, and convey them to a separator for separating the material into defined components. The material in the drum of a truck mixer, for which no further use can be found, is emptied into the feeding device. In this procedure the drum of the truck mixer is usually cleaned internally with up to 2 m.sup.3 of water in order to prevent caking of the residual material on the inside of the drum.
WO 94/00634 discloses a feeding device of this type, which comprises a receiving trough for the material, in which a conveying screw is rotatably disposed. The feeding device communicates, via a passage in the lower region of the end wall of the receiving trough, with a separator which is filled with water in its lower region. Starting from an appropriate level of filling, the washing water is able to flow unhindered back and forth through this passage between the separator and the feeding device. Rotation of the conveying screw conveys the residual material from the feeding device into the separator. If too large an amount of residual material and washing water are introduced into the feeding device too rapidly, the displacement results in excessive flow rates of the washing water within the separator as well, thereby entraining a large quantity of fines from the separator into a stir tank from which the washing water is withdrawn in order to produce fresh concrete. This may breach the water density limit, owing to the entrained fines, so that the washing water in the stirred tank can no longer be used for concrete production. The 30 to 50 m.sup.3 of washwater in the stirred tank then have to be disposed of, which entails high costs. In addition, fines settle on the floor of the stirred tank, despite use of a stirring apparatus. If the height of the sludge layer reaches a certain level, the stirred tank must be emptied, and the solid deposits have to be removed using a compressed-air hammer and then likewise disposed of.
It has been further found that when very liquid residual material, such as concrete, is introduced, it behaves like water. Owing to the design of the known feeding device, the residual material flows uncontrolled into the separator independently of the rotary speed of the conveying screw, and it may overload the separator. Upon an overload which leads to deterioration in the separation efficiency, the separator switches off and the material (residual concrete, residual mortar) has to be removed manually from the separator. In addition, an overload may damage the separator. Since emptying the truck mixer generally takes place at the end of a working day and since ready-mixed concrete plants, or at least fairly large ones, have a number of truck mixers, this often produces considerable waiting times at the feeding device and the separator, which is not only associated with high costs owing to the overtime of the drivers and the operators but also results in the residual material and the washwater frequently being too rapidly emptied into the feeding device, and so inducing the above-mentioned disadvantages.
A further disadvantage associated with the known feeding device is that the base of the receiving trough must be disposed at the same depth as, or deeper than, the exit of the separator for the washwater, and the exit is connected to the stirred tank. As a result, constructional measures, for example, a concrete pit, are necessary for the depth construction of the separator.